1. Field of the Invention
The present invention relates generally to an interferometric arrangement for measuring the contour of a reflective surface, and more particularly pertains to an arrangement of the aforementioned type for providing a recording which is a full development of the contour of a surface which may be an internal or external, linear or non-linear surface such as a cylindrical or conical surface.
2. Discussion of the Prior Art
The prior art has recognized for years the problems of providing interferometric data on the contour of a cylindrical or conical reflective surface, but heretofore has not provided an arrangement which is capable of making such measurements.
Montagnino U.S. Pat. No. 4,022,532 discloses an interferometer arrangement for measuring the contour of an optical surface in which a laser unequal path interferometer has a measuring beam and a reference beam. Reflective spots are mounted at a number of sample points on the surface, and the measuring beam is focused by an optical system to provide an image field that includes the reflective spots, which are oriented to reflect light from the measuring beam back to the optical system to form a conjugate image of the field of spots on photodetectors. The reference beam, the path length of which is modulated, is combined with the light reflected from the spots to the photodetectors. Separate detectors measure the intensity of the combination of the reference beam light and measuring beam light reflected from at least two different spots at one time. A shift in the position of one sample point forward or back in relation to another sample point, which is a reference point, is thus monitored by comparing the phase relationship of the combination of the reference light with reflected light derived simultaneously from at least a pair of the sample points.
Although the arrangement disclosed by this patent utilizes a laser unequal path interferometer, the actual measuring arrangement is quite different from the present invention, and does not provide an interferometric recording which is a full development of the contour of a reflective surface.